The disclosure of Japanese Patent Application No. 2000-078954 filed on Mar. 21, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to controlling the torque of an internal combustion engine installed in a vehicle or the like and, more particularly, to controlling the torque of an internal combustion engine having valve mechanisms for driving opening and closing intake and exhaust valves in their opening and closing directions by an electromagnetic force.
2. Description of Related Art
In recent years, mainly for the purpose of preventing a mechanical loss resulting from the driving of intake and exhaust valves in their opening and closing directions, preventing a pumping loss of intake air, and enhancing the net thermal efficiency in an internal combustion engine installed in a vehicle or the like, the development of a valve mechanism capable of arbitrarily changing timings for opening and closing intake and exhaust valves has been promoted.
Electromagnetic driving valve mechanisms are known. Some of these mechanisms have an armature made of a magnetic material that reciprocate in an interlocking relationship with intake and exhaust valves, a closing electromagnet attracting the armature in its closing direction upon application of an exciting current, an opening electromagnet attracting the armature in its opening direction upon application of an exciting current, a closing-side return spring urging the armature in its closing direction, and an opening-side return spring urging the armature in its opening direction.
According to such an electromagnetic driven valve mechanism, there is no need to drive intake and exhaust valves in their opening and closing directions by the turning force of an engine output shaft (crank shaft) as is the case with a conventional valve mechanism. Therefore, the loss of the engine output resulting from the driving of the intake and exhaust valves is prevented.
Furthermore, according to an electromagnetic driving unit as mentioned above, there is no need to drive intake and exhaust valves in their opening and closing directions in an interlocking relationship with the rotation of an engine output shaft as is the case with a conventional valve mechanism, and the intake and exhaust valves can be opened and closed at arbitrary timings by changing the timings when an exciting current is applied to an opening electromagnet and a closing electromagnet. Therefore, it is possible to control the amount of intake air in each cylinder without employing an intake throttle valve (throttle valve). As a result, the possibility of the pumping loss of intake air resulting from the throttle valve is eliminated.
On the other hand, in an electromagnetic driving valve mechanism as mentioned above, it is also important to precisely control the combustion pressure generated during combustion of a mixture in each cylinder, namely, the torque generated in each cylinder in accordance with the operation state of an internal combustion engine, the running condition of a vehicle and the like.
In order to meet such demands, Japanese Patent Application Laid-Open No. 10-37727 proposes a device for controlling intake and exhaust valves in a multi-cylinder engine. The device, electromagnetically operating intake and exhaust valves, disposed in each cylinder of an internal combustion engine, are automatically controlled to be opened and closed in accordance with an operation state of the engine. The device is designed to ensure the leveling of the torques generated in all the cylinders by correcting the timings for the opening and the closing of the intake or exhaust valves such that an equal amount of intake air is sucked into each cylinder.
In a device for controlling intake and exhaust valves in a multi-cylinder engine as mentioned above, the torque of the internal combustion engine is controlled as a whole while ensuring the leveling of the torques in all the cylinders. Thus, in the case where the torque of the internal combustion engine is increased or reduced as a whole, the torques in all the cylinders are increased or reduced en bloc. Because the amount of an increase or a decrease in the torques tends to be great, an acceleration-deceleration shock may be caused.
Further, torque control of the internal combustion engine is not linked with gear-change operation of a transmission in the vehicle, and an acceleration-deceleration shock may be caused by gear-change of the transmission.
It is an object of the invention to provide a method and an apparatus to realize high-precision torque control adapted for an operation state of an internal combustion engine and/or a running condition of a vehicle by providing individual control of the torques in cylinders of an internal combustion engine having valve mechanisms that drive intake and exhaust valves in their opening and closing directions by an electromagnetic force.
It is another object of the invention to provide a method and an apparatus to realize high-precision torque control in an internal combustion engine having valve mechanisms that drive intake and/or exhaust valves in their opening and closing directions by an electromagnetic force by performing torque control of the internal combustion engine in accordance with an operation state of a transmission.
An internal combustion engine having valves according to a first aspect of the invention comprises electromagnetic driving valve mechanisms that drive the intake and exhaust valves of the internal combustion engine in their opening and closing directions by means of an electromagnetic force, a target cylinder torque calculator that calculates a target cylinder torque required of one cylinder in accordance with a target engine torque required of the internal combustion engine, a valve timing determiner that determines timings for the opening and the closing of the intake and/or exhaust valves in accordance with the target cylinder torque calculated by the target cylinder torque calculator, and a valve controller that controls the electromagnetic driving valve mechanisms in accordance with the timings determined by the valve timing determiner.
In an internal combustion engine having valves thus constructed, if a target engine torque is determined with the operation state of the internal combustion engine, the running condition of a vehicle equipped with the internal combustion engine and the like being used as parameters, a target cylinder torque required of one cylinder is calculated based on the target engine torque, and the timings for the opening and the closing of the intake and/or exhaust valves are determined in accordance with the target cylinder torque.
In this case, the intake and/or exhaust valves in each cylinder are driven in their opening and closing directions at the timings determined based on the target cylinder torque required of one cylinder, and each cylinder generates a torque corresponding to the target cylinder torque. In other words, the torque of the internal combustion engine is controlled based on the individual control of the torques in the cylinders.
As a result, the torque of the internal combustion engine is finely controlled. For example, in the case where the torque of the internal combustion engine is increased or reduced, it is also possible to increase or reduce the torque of the internal combustion engine linearly by gradually increasing or reducing the torques in the respective cylinders according to the combustion sequence (ignition sequence).
The target cylinder torque calculator may individually calculate target cylinder torques for all of the cylinders of the internal combustion engine. In this case, the valve timing determiner individually determines the timings for the opening and the closing of the intake and/or exhaust valves of all the cylinders in accordance with the target cylinder torques individually calculated by the target cylinder torque calculator.
The target torque of the internal combustion engine is obtained by correcting a base target torque that is determined using the engine load, the speed of the internal combustion engine and the like as parameters, in consideration of various correction factors.
For example, the aforementioned correction factors include an acceleration-deceleration shock absorbing torque for absorbing an acceleration-deceleration shock generated in conjunction with gear-change operation of an automatic transmission (A/T), an acceleration-deceleration shock absorbing torque for absorbing an acceleration-deceleration shock that is generated when an auxiliary operated by part of the output of the internal combustion engine, such as a compressor for an air-conditioner is switched between its operative state and its inoperative state, an acceleration-deceleration shock absorbing torque for absorbing an acceleration-deceleration shock generated based on the magnitude of moment of inertia of a continuously variable transmission (CVT), and a deceleration shock absorbing torque for absorbing a shock generated in conjunction with deceleration control that is performed when the running speed of a vehicle equipped with the internal combustion engine reaches a predetermined upper limit value.
In the aforementioned aspect, a fuel injection controller for determining a fuel injection amount and/or a fuel injection timing for each of the cylinders in accordance with the target cylinder torque calculated by the target cylinder torque calculator can be provided. If the timings for the opening and the closing the intake and/or exhaust valves in each of the cylinders are determined in accordance with the target cylinder torque, the amounts of intake air in the respective cylinders may be different from one another. Therefore, in such a case, the amount of fuel injection needs to suit the amount of intake air in each of the cylinders.
In the aforementioned aspect, an intake throttle valve can be disposed in an intake passage of the internal combustion engine to adjust an amount of air flowing through the intake passage and a valve opening degree determiner can be provided for determining an opening degree of the intake throttle valve in accordance with the target cylinder torque calculated by the target cylinder torque calculator.
In this case, it becomes possible to use the valve mechanisms in combination with the intake throttle valve to control the amount of intake air in the internal combustion engine, namely, the load applied to the internal combustion engine, and guarantee a precise amount of intake air that is required of each cylinder to achieve the target cylinder torque.
In addition to the aforementioned components, that is, the valve mechanisms, the target cylinder torque calculator, the valve timing determiner and the valve controller, the internal combustion engine according to the invention may further comprise an intake manifold negative pressure detector for detecting an intake manifold negative pressure generated in an intake passage of the internal combustion engine.
In this case, the valve timing determiner determines timings for the opening and closing the intake and/or exhaust valves based on the target cylinder torque calculated by the target cylinder torque calculator and the intake manifold negative pressure detected by the intake manifold negative pressure detector. This is because the torque of the internal combustion engine is controlled while supplying a predetermined intake manifold negative pressure to a system operating based on the intake manifold negative pressure, such as a brake booster constituting a braking system of the vehicle, an exhaust gas recirculation system (EGR system) for returning part of the exhaust gas in the internal combustion engine to the intake system, and the like.
An internal combustion engine according to a second aspect of the invention comprises valve mechanisms that drive at least one of intake and exhaust valves of the internal combustion engine in their opening and closing directions by means of an electromagnetic force, a transmission capable of changing a gear change ratio, and a controller that controls one of the valve mechanism and the transmission in accordance with the an operation state of the other valve mechanism and the transmission.
According to the above-mentioned second aspect, one of the e valve mechanism and the transmission is controlled in accordance with an operation state of the other of the valve mechanism and the transmission. Therefore, it is possible to further improve the driveability.
The controller may control the valve mechanism, and may control opening characteristics of at least one of the intake and exhaust valves in accordance with an operation state of the transmission. According to this aspect, it is possible to absorb an acceleration-deceleration shock resulting from gear-change operation of the transmission, and further improve the driveability.